Study On Spectrum Handoff Technology In Cognitive Radio Systems

Wireless spectrum resource is natural and limited. With the rapid development of wirelesscommunication technology and its increasing spectrum demand, spectrum shortage problem isgetting worse. However, the real reason for this paradox is that the available spectrum resourceshave not been fully utilized. The concept of Cognitive Radio was proposed, which is a good idea forsolving this problem. In cognitive radio, the authorized users’ idle spectrum can be lent to cognitiveusers temporarily. In this way, the unused spectrum can be used effectively by cognitive users whilewithout affecting the authorized users. So the scarce of the spectrum resources issues can be solvedeffectively.Because the available wireless spectrum is dynamic, the cognitive users must make decisionstimely based on the channel states. On one hand, we need to protect the primary users’ servicequality first, on the other hand, we try to maintain and ensure the communication needs of thecognitive users. This is what this paper will focus on: Study on the spectrum handoff technology incognitive radio system.Firstly, we introduce the related theory of cognitive radio and discuss the spectrum handofftechnology in cognitive radio, including its concept, strategies, analysis model, and the targetchannel selection algorithm as well.Secondly, we analysis the performance of the cumulative handoff delay based on reactivespectrum handoff strategies. For cognitive users with the same priority, we simulate and analysis thechanges of cumulative handoff delay by changing some the related factors. Then for cognitive userswith different priorities, the cognitive users with higher-priority can seize the channels prior to thelower-priority cognitive users’. We then compare the cumulative handoff delay of the two types ofcognitive users with the same parameters. Simulation results show that the higher-priority cognitiveusers have a lower average cumulative handoff delay than the lower-priority cognitive users.Finally, we analysis the performance of the cumulative handoff delay based on proactivespectrum handoff strategies. The changes of cumulative handoff delay by changing some relatedfactors are firstly studied. Then the two types of spectrum handoff strategies are compared oncumulative handoff delay, simulation results show that the reactive spectrum handoff with smaller sense time has a lower average cumulative handoff delay than the proactive spectrum handoff, butwith the increasing of sense time, the proactive spectrum handoff will have a better performance oncumulative handoff delay.